Wim Distelmans, a cancer specialist who carried out the euthanasia on Monday, is the same doctor who last year gave lethal injections to congenitally deaf twins who were frightened they were also going blind.

Explaining his decision hours before his death, Mr Verhelst said he was "the girl that nobody wanted".

He told Het Laatste Nieuws newspaper: "While my brothers were celebrated, I got a storage room above the garage as a bedroom. 'If only you had been a boy', my mother complained. I was tolerated, nothing more."

Mr Verhelst had hormone therapy in 2009, followed by a mastectomy and surgery to construct a penis last year. However, "none of these operations worked as desired", he said. "I was ready to celebrate my new birth, but when I looked in the mirror, I was disgusted with myself. My new breasts did not match my expectations and my new penis had symptoms of rejection. I do not want to be a monster."

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He informed his family of his death by letter. "I had happy times, but the balance is on the wrong side," he said.

Prof Distelmans said: "He was in a situation with incurable, unbearable suffering. Unbearable suffering for euthanasia can be both physical and psychological."

Mr Verhelst's death will revive Belgium's debate over medical euthanasia as statistics show a 25 per cent increase this year, to 1432, in the number of cases. The country is one of only three in Europe, along with Holland and Luxembourg, that allows the practice.